The present invention relates to a cutter bit for drills, and more particularly relates to a new and improved construction for a cutter bit for drills of the type used in roof drilling in coal mines or the like. Heretofore, conventional drills, such as those employed for drilling holes in the roofs of mine shafts for installing roof bolts or receiving explosive charges, generally comprise elongated, hollow drill rods adapted to be connected to a source of rotary power. Generally, the upper free end of the drill rod has mounted a cast or forged cutter bit including a head portion to which is permanently attached a plate-like insert element, such as of carbide or the like. Because of the fact that drilling in rock formations produces large quantities of drill cuttings and dust, it has been the practice to remove these materials by means of holes or openings provided in the walls of the hollow drill rod beneath the cutter drill bit, and drawing this material into the drill rod using a suitable vacuum pump to draw in the dust-laden air, or alternatively, by forcing a coolant liquid up through the drill rod and out through the holes to thereby wash away the chips and dust. More recently, because of the number of problems with such type of arrangements, it has now been known to make the cutter bit of a hollow interior construction with dust collecting holes or openings being formed in the cutter bit beneath the carbide insert so that the carbide insert is more nearly adjacent to the area in which the dust is formed for greater efficiency in dust collection. One such prior drill bit is commercially available under applicant's trademark "DUST HOG". This bit has good performance characteristics in that it runs cooler, penetrates faster and lasts longer than conventional bits in dry drilling applications, such as disclosed for example in U.S. Pat. No. 3,613,807 and No. 3,187,825. For further examples of drill bits having the features of dust collecting holes or openings reference may be had to U.S. Pat. Nos. 3,434,553 and 3,434,554.
Though such conventional "DUST HOG" drill bits have overcome many, if not all, of many problems attendant in prior bits for use in dry drilling applications, it has been recently discovered that the conventional "DUST HOG" bits are not as efficient for drilling in soft rock formations. For example, it has been found that in drilling in soft rock at a fast rate of penetration, this type of cutter bit creates more cuttings than can be carried and removed through the interior of the drill rod. These cuttings then clog and pack the drill rod causing dust puffing or stoppage. For example, in drilling through shale, the shale cuttings usually break-up into different sized chunks. These chunks then tend to block the holes or openings provided in such prior cutter bits.
Accordingly, the present invention has provided a new and improved cutter bit which overcomes the problems attendant in prior conventional bits utilized in dry drilling operations. More specifically, the cutter bit of the present invention greatly enhances the flexibility and performance characteristics for a wide variety of drilling applications, and which is particularly suited for drilling in soft rock formations typically found in drilling roof top strata. In such strata it has been discovered that the cutter bit of the present invention not only minimizes drill rod clogging but also the bit cuts at a faster rate which also increases the length of the bit life by generally the same ratio. In addition, it has also been found that the drill string employed with the cutter bit of the present invention does not stick in the drilled hole indicating that a straighter hole has been drilled as compared to conventional solid head drill bits. In addition to good performance characteristics in hard, medium as well as soft top rock formations, the cutter bit of the invention has been found to provide good drilling characteristics in irregular top rock formations where extensive breakage has been experienced with previous type drill bits.
Moreover, the present invention provides a new and improved cutter bit which has good performance characteristics in hard, medium and irregular rock formations, and improved performance characteristics in soft rock formations providing a cutter bit which is believed, for the first time, to have in fact, relatively universal application. Other more specific advantages of the present cutter bit include its ability to provide a stronger and more stable support for the carbide cutter blade or element. Also, the cutter bit by its construction and design has a hefty configuration so as to minimize, if not prevent, breakage. Further, the cutter bit of the present invention can be easily fabricated and at reduced cost by reason of the elimination of hard to machine dust collection parts and by having less heel to grind off during fabrication. In essence, the cutter bit of the invention incorporates all of the advantages of applicants "DUST HOG" (i.e. runs cooler, penetrates faster and lasts longer than conventional bits) through the use of especially designed dust collection holes that are disposed in close proximity to the carbide cutting (edge) element.